Is there a common Twitter hashtag for D?
If there isn't any, how about #dlang?
#D and #DMD give too many false positives,
#D_programming_language is ridiculously too long.
I guess that Twitter is not very popular among D fans
(http://www.digitalmars.com/d/archives/digitalmars/D/announce/Anyone_use_twitter_for_D_14287.html)
, and that serious discussions should be kept in newsgroups.
On the other hand, I don't see anything wrong with posting simple tweets
like "new DMD release, yay!" on Twitter.
It's a small contribution to what Walter called "social proof" :-)

Not popular!
JarrettB
h3r2tic
yigal100
OctarineParrot
asterite
komma8komma1
jcarrascal
boorad
aldacron
shinh
baxissimo
larsivi
WalterBright
Just in my following list (other than myself of course) ;)
Now I can't really say how _active_ they are.. though Walter does
usually announce new compiler versions.